For the colour printing of your digital files, you must supply the graphics and images in the right colour mode. Most of the software programs will allow you to work with RGB colour or CMYK colour mode. RGB colours or Red-Green-Blue colours are known as the primary colours of the light. This colour combination can be seen on your television or computer monitors. Digital cameras and scanners also create pictures with Red-Green-Blue colour combinations. Red-Green-Blue colour mode ought to be used while taking photos that are to be viewed on the monitor, or by emails or CD.
All colours of the light spectrum are created from the primary colours, but monitors can display only a limited colour range from the spectrum able to be seen. Light is sent from the monitor, and the printing ink recognises only a certain wavelength of colours. The three primary colours are combined to create white colour. If the three primary colours are missing, the light will show as black. By combining various intensities of RGB colours, each combination results in differing colours. A monitor of a television or a computer is made of small units known as pixels. Every pixel contains three units of light, and each unit represents red, green and blue.
We can not see the individual pixels with the naked eye because they are so tiny. Each pixel is created by applying proper values of RGB, and without the proper values of the colour units, you cannot see anything displayed on the screen. The values of RGB colours are calculated mainly by three methods. The first method is to set them with the help of different numeric values. The numeric values used for this purpose are the values from 0 to 255, and this is the easiest method of the three.
The second method is the use of hexadecimal notations. This method is mainly used for HTML and other languages of the computer. These notations follow a logical pattern. The hexadecimal notation uses six characters, with these characters being divided into three. The first pair represents the red, the second pair green and the third pair as blue. Each pair is represented by a hexadecimal number (0-9) and the letters (A-F). The third method is the percentage in which a certain percentage represents each colour. The program translates these percentages into suitable values ranges from 0-255.
CMYK colours or Cyan-Magenta-Yellow colours are subtractive colours, whereas RGB colours are additive colours. Additive colours refer to light, whereas subtractive colours refer to inks, paint or pigment. CMYK mode is used for printing as all kind of printers are using subtractive colours to result in differing colours. When three additive colours are combined, the combination will produce white colour. But when three subtractive colours are combined, the combination produces black. This difference develops a large diversity between the resulting print and the onscreen display. Additive colour throws the light from the monitor, and if more light is projected from an independent pixel, it will be closer to the pure light. In the case of printer inks, they absorb light and reflects only the wavelengths of light that is associated with the colour of the ink.
The inks of the printer take away the non-essential wavelengths from the light that falls on the ink. The remaining light will return to the eye, resulting in the impression of other colours. If you are mixing a number of colours, then more light will be absorbed by the ink and a lesser amount of light will be reflected to the eye, which results in darker colour. Black ink produced by the CMYK colours is not the deep black. You have to add black ink to produce the best results for printing true black. To receive a darker tone of any colour, you have to add black in CMYK mode.
What about the lighter shade of colours? As white ink cannot be created using CMYK colours, you need to work under the hypothesis that you are printing the colours onto white paper. Because tiny dots of inks are used to print images you have to use the inks in lower percentage to receive lighter shades so that more white colour is visible among the dots. The values of CMYK colours are calculated with the help of four different percentages. The values of each percentage should be between 0 and 100 so that the total percentage of the ink values can be up to 400%. But if the total percentage reaches 400%, the ink will take more time to dry. Hence, the total percentage of the ink shouldn’t be more than 300% in CMYK mode.
Both the colour modes have limitations. Images developed using RGB mode can’t be converted smoothly into CMYK mode due to the brightness of RGB colours. Similarly, CMYK colours cannot be translated to RGB mode as the sharp look of RGB colours is missing in CMYK mode online. This is the reason why RGB colours are used in monitors and CMYK colours are used in printers.